PDAs are small, substantially hand-held computers that are used for storing, manipulating and retrieving data. One example of a PDA is the Palm Pilot® manufactured by 3Com Corporation. PDAs provide a variety of functions, such as an electronic day planner, an address book, a to do list, and a memo pad.
Electronic navigation devices employing Global Positioning System (“GPS”) receivers are known. The GPS includes a plurality of satellites that are in orbit about the Earth. The orbit of each satellite is not necessarily synchronous with the orbits of other satellites and, in fact, is likely asynchronous. The GPS receiver device receives spread spectrum GPS satellite signals from the various satellites. The spread spectrum signals continuously transmitted from each satellite utilize a highly accurate frequency standard accomplished with an extremely accurate atomic clock. Each satellite, as part of its data signal transmission, transmits a data stream indicative of that particular satellite. The GPS receiver device acquires spread spectrum GPS satellite signals from at least three satellites to calculate its two-dimensional position by triangulation. Acquisition of an additional signal, resulting in signals from a total of four satellites, permits the GPS receiver device to calculate its three-dimensional position. In this manner, an electronic navigation device employing a GPS receiver has the ability to accurately compute the position of the device in real time, even as the device moves. One example of an electronic navigation device is the eMAP portable electronic map manufactured by Garmin International.
Plug-in GPS receiver modules for PDAs are known. There are problems associated with various plug-in GPS receiver modules and PDAs. One problem is that a PDA with a plug-in GPS receiver module is cumbersome to handle and use. Two separate devices must be handled. Additionally, the plug-in GPS receiver module and the PDA do not function together to provide integrated PDA features.
Therefore, there exists a need for a PDA that incorporates GPS receiver technology within a single module, and that further integrates GPS capabilities into PDA functions such that the GPS capable PDA is not cumbersome to handle or to use.